U1540 on Cadillac
Body Control Module Lost Communication With Right Rear Window Motor on LIN Bus
U1540 on Cadillac vehicles indicates body control module lost communication with right rear window motor on lin bus. Au7o has documented this code across 1 Cadillac model — most commonly on XTS. Manufacturer-specific (General Motors — Buick, Cadillac, Chevrolet, GMC). The body control module stopped receiving the supervised periodic messages it expects from the right rear power window motor module over the single-wire LIN serial data bus. The usual symptom is the right rear window not responding to the switch, working intermittently, or losing its express-up/anti-pinch function. It is a comfort-system fault, not a drivability or safety fault. Typical repair costs on Cadillac range from $200 to $900, depending on the specific model and root cause.
Common Causes of U1540
- •Failed right rear window motor / regulator module
- •Open, short, or high resistance in the LIN circuit to the door
- •Damaged wiring in the door-jamb harness boot from repeated door movement
- •Corroded or backed-out connector terminals at the motor or door module
- •Loss of battery power or ground to the window motor module
- •Faulty body control module
U1540 on Cadillac by Model
Cadillac XTS(1 issue)
- Parasitic Battery Drain / Modules Not Entering Sleep Mode2013-2019
XTS owners frequently report the 12V battery going dead overnight or after a few days of sitting, caused by a control module failing to enter sleep mode and continuing to draw current with the ignition off. Common culprits on this platform include the radio/CUE (infotainment) module and the BCM. Repeated deep discharges then prematurely kill the battery and can trigger low-state-of-charge warnings and start-stop faults. GM issued service information for low-battery-state-of-charge conditions on 2018-2019 XTS/ATS/CTS.
Looking for U1540 on a different make?
View U1540 across all makes →Frequently Asked Questions
What does U1540 mean on Cadillac?▼
U1540 stands for "Body Control Module Lost Communication With Right Rear Window Motor on LIN Bus." Manufacturer-specific (General Motors — Buick, Cadillac, Chevrolet, GMC). The body control module stopped receiving the supervised periodic messages it expects from the right rear power window motor module over the single-wire LIN serial data bus. The usual symptom is the right rear window not responding to the switch, working intermittently, or losing its express-up/anti-pinch function. It is a comfort-system fault, not a drivability or safety fault. On Cadillac specifically, this code is documented across 1 model.
What causes U1540 on Cadillac vehicles?▼
Common causes on Cadillac: Failed right rear window motor / regulator module, Open, short, or high resistance in the LIN circuit to the door, Damaged wiring in the door-jamb harness boot from repeated door movement, Corroded or backed-out connector terminals at the motor or door module, Loss of battery power or ground to the window motor module. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix U1540 on a Cadillac?▼
Repair costs on Cadillac range from $200 to $900, depending on the specific model and root cause.
Which Cadillac models have U1540 documented?▼
Au7o has documented U1540 on 1 Cadillac model: XTS.